Pressure-sensing switches typically have a pressure-sensing region and an electrical region, with pressure information from the pressure region being communicated to the electrical region. When a pressure-sensing switch is designed for use in a hazardous environment, e.g. for monitoring gasoline vapor vacuum pressure or detecting pressure differential in a gasoline vapor flow, it is critical that the electrical region of the switch be sealed against penetration of explosive gasoline vapor from the pressure region. Typically, the necessary sealing may be provided by diaphragm displacement indication through mechanical means, with static or dynamic seals or flexible membrane devices.